Avd hardmask for damascene patterning

ABSTRACT

A method including forming a dielectric layer on a contact point of an integrated circuit structure; forming a hardmask including a dielectric material on a surface of the dielectric layer; and forming at least one via in the dielectric layer to the contact point using the hardmask as a pattern. An apparatus including a circuit substrate including at least one active layer including a contact point; a dielectric layer on the at least one active layer; a hardmask including a dielectric material having a least one opening therein for an interconnect material; and an interconnect material in the at least one opening of the hardmask and through the dielectric layer to the contact point.

BACKGROUND

1. Field

Integrated circuit processing.

2. Description of Related Art

Modern integrated circuits use conductive interconnections to connectthe individual devices on a chip and/or to send and/or receive signalsexternal to the device(s). Common types of interconnections includecopper and copper alloy interconnections (lines) coupled to individualdevices, including other interconnections (lines) by interconnectionsthrough vias. It is not uncommon for integrated circuit to have multiplelevels of interconnections (e.g., five or six levels) separated bydielectric materials. In prior integrated circuit structures, a populardielectric material for use as an interlayer dielectric (ILD) wassilicon dioxide (SiO₂). Currently, efforts are focused on minimizing theeffective dielectric constant of an ILD so materials having a dielectricconstant lower than SiO₂ (low k dielectric material) have garneredsignificant consideration. Many of these materials, such as carbon,silicon, oxygen based materials are porous.

Developing and implementing low k ILD based integrated circuits mayutilize complementary and compatible photolithography and etchingprocesses to pattern devices that will not attack underlying layerscritical to device performance. Representatively, Contacts made out ofTungsten are used, for example, as vertical interconnects between thesource/drain junction of transistor devices and the first levelinterconnect, which typically consists of a dual damascene metal and avia used to connect to the contact layer in multilevel interconnectschemes. Current post patterning cleaning schemes as applied to a firstdual damascene metal layer (M1/V0) deposited on a contact have agenerally narrow process window due to the requirements of being able toremove both the metal hard mask (e.g., titanium or titanium nitride),photoresist, and residual etch polymer while simultaneously not etchingtungsten (in the contact exposed thru the V0), copper or the low k ILD.

One process to form a first dual damascene metal level (M1) on anintegrated circuit structure uses a titanium nitride hard mask to createa dual damascene M1V0 about a tungsten plug. The titanium nitride hardmask is conductive and therefore must be removed to avoid line-to-lineshorting. Wet clean chemistries have not been identified that can striptitanium nitride without also damaging the tungsten contact layer. Toaddress this issue, one solution is that after the M1V0 patterning andprior to titanium nitride removal, a sacrificial light absorbingmaterial (SLAM) is deposited and dry etched for use as a layer toprotect the underlying tungsten during the titanium nitride wet clean.This method can be costly and tends to increase the M1V0 criticaldimensions due to multiple process steps which can lead to V0 to wrongcontact shorting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic cross-sectional side view of a portion of acircuit structure including a contact point, an etch stop layer over thecontact point followed by an interlayer dielectric (ILD) and two hardmasks.

FIG. 2 shows a structure of FIG. 1 with the introduction of aphotoresist material to trench pattern the hard masks.

FIG. 3 shows the structure of FIG. 2 following the formation of trenchesand the removal of the photoresist material and the optional removal ofone hard mask.

FIG. 4 shows the structure of FIG. 3 following the introduction of asacrificial material over the structure and the introduction of aphotoresist material patterned to define one or more vias.

FIG. 5 shows the structure of FIG. 4 following the opening of vias tounderlying contact points.

FIG. 6 shows the structure of FIG. 5 following the removal of thesacrificial light absorbing material and the photoresist material andthe introduction of a conductive material in the trenches and vias.

FIG. 7 shows a top view of the structure of FIG. 6.

FIG. 8 illustrates a schematic illustration of a computing device.

DETAILED DESCRIPTION

FIG. 1 shows a cross-sectional side view of a portion of an integratedcircuit structure, such as a portion of a microprocessor chip on asilicon die at a point in the process of forming interconnection to adevice, including possibly to other interconnections. A typicalintegrated circuit structure such as a microprocessor chip may have, forexample, multiple interconnection layers or levels separated from oneanother by interlayer dielectric (ILD) material. Referring to FIG. 1,structure 100 includes substrate 110 which may be the wafer substrate(e.g., a portion of a silicon wafer) having circuit devices, includingtransistors, thereon as well as one or more levels of interconnection todevices. FIG. 1 shows contact point 120 that may be a circuit deviceformed in or on a substrate (e.g., a silicon substrate) or aninterconnection line formed above the wafer to devices on the wafer. Itis appreciated that the techniques described herein may be used forvarious interconnections within an integrated circuit including todevices that include circuit devices and other interconnections. In thissense, contact point 120 represents such devices or interconnectionswhere an interconnection contact may be made.

Overlying substrate 110 in FIG. 1 is etch stop layer 130 of a materialsuch as silicon nitride (Si_(x)N_(y)) or silicon carbon nitride (SiCN).Overlying etch stop layer 130 is dielectric layer 140 which is, forexample, an ILD. A representative material for dielectric layer 140 is amaterial having, for example, a dielectric constant (k) less than thedielectric constant of silicon dioxide (SiO₂) (e.g., a “low k”material). Representative low k material includes materials containingsilicon, carbon and oxygen which may be referred to as polymers and thatare known in the art. In one embodiment, dielectric layer 140 is porous.

Overlying dielectric layer 140 in FIG. 1 is first hard mask 150. In oneembodiment, first hard mask 150 is a dielectric material. Suitabledielectric materials for hard mask 150 include materials having, forexample, a dielectric constant (k) greater than a dielectric constant ofSiO₂ (e.g., a “high k” material). Suitable materials are also thosematerials that have a density greater than a material for dielectricmaterial 140 and have a etch selectivity relative to a material fordielectric layer 140 (e.g., can be etched at a different rate than orexclusive of a material for dielectric layer 140). Representativematerials include silicon oxynitride, hafnium oxide, zirconium oxide,hafnium silicate, hafnium oxynitride, lanthanum oxide, aluminum oxideand similar high dielectric constant materials. In one embodiment, hardmask 150 is deposited, for example, by a plasma deposition process, to athickness to serve as a mask to underlying dielectric layer 140 (e.g.,to protect from undesired modification of the dielectric material fromenergy used in subsequent mask registration). In one embodiment, arepresentative thickness is a thickness that will not significantlyeffect an overall dielectric constant of the ILD (dielectric layer plushard mask 150) but at most will marginally effect such overalldielectric constant. In one embodiment, a representative thickness is onthe order of 30 angstroms (Å)±20 Å. In another embodiment, arepresentative thickness is on the order of two to five nanometers (nm).

Overlying hard mask 150 in structure 100 of FIG. 1 is optional hard mask160. Hard mask 160, in one embodiment, is a conductive material such assilicon nitride, titanium nitride or titanium. It is appreciated that,as it is optional, second hard mask 160 need not be present. If present,a representative thickness of second hard mask 160 is on the order of 20nanometers.

FIG. 2 shows the structure of FIG. 1 following the deposition andpatterning of photoresist material 170. In this embodiment, photoresist170 is patterned to define opening 175 over second hard mask 160 toallow patterning of hard mask 160 and hard mask 150 for exposure todielectric layer 140 for a trench opening.

FIG. 3 shows the structure of FIG. 2 following the opening of trenchesthrough dielectric layer 140 and the removal of photoresist material170. FIG. 3 also shows structure 100 following the removal of optionalhard mask 160. In one embodiment, a hard mask of silicon nitride may beremoved with a wet clean chemistry.

FIG. 4 shows the structure of FIG. 3 following the deposition of asacrificial material (e.g., SLAM, BARC) on the structure and over hardmask 150 and into trench 200. Sacrificial material 210 is deposited to athickness greater than the depth of trench 200 to provide a planarsurface. Following the deposition of sacrificial material 210,photoresist material 220 is deposited and patterned to include opening230 for via formation. Referring to FIG. 4, it is noted that thepatterning of photoresist 220 to define opening 230 does not need to beprecise. The presence of hard mask 150 will inhibit etching intodielectric layer 140 in areas protected by the hard mask. In thismanner, a self-aligned process for forming vias 250 is described.

FIG. 5 shows via 250 formed through dielectric layer 140 and etch stoplayer 130 to contact points 120.

FIG. 6 shows the structure of FIG. 5 following the removal ofphotoresist layer 220 and sacrificial material 210 and the deposition ofa conductive material such as copper in trench 200 and via 250. Asuitable conductive material for trench 200 and via 250 is copper or acopper alloy deposited by an electroplating process. It is appreciatedthat the via and trench may be lined with a barrier layer or an adhesionlayer. Suitable materials for barrier layer include but are not limitedto a refractory material such titanium nitride, tungsten nitride,tantalum or tantalum nitride. Suitable materials for an adhesion layerinclude but are not limited to titanium, tantalum and ruthenium.Further, a suitable seed material may be deposited prior to theintroduction of the copper or copper alloy conductive material. Suitableseed materials for a deposition of copper interconnection materialinclude copper, nickel, cobalt and ruthenium. FIG. 6 also shows thathard mask 150 remains after the formation of via 250 and trench 200 andmay optionally be retained as a permanent part of structure 110. Inanother embodiment, hard mask 150 is removed after via 250 is formed.FIG. 7 shows a top view of structure 100 and illustrates trench 200 andvia 250 each filled with a conductive material. Adjacent trench 200 andvia 250 is a corresponding trench of conductive material. It isappreciated that additional interconnection layers may be formed on theinterconnection layer shown in structure 100 to other contact pointsincluding, but not limited to, underlying devices, includinginterconnection lines.

In the above embodiment, full trench depths were formed, followed byremoval of the optional hard mask of a conductive material (hard mask160), and full via depth to a contact point. In another embodiment, thisprocess may be modified by, for example, forming the via to a partialdepth prior to removing the optional hard mask of conductive material.In this manner, the remaining dielectric material beyond the partial viadepth will protect the contact point (e.g., contact point 120) frompossible damage during removal of the optional hard mask of conductivematerial. Another modification that may be combined with the describedpartial via depth modification process is a partial trench depthmodification where the trench is formed to a partial depth, the via isformed to a partial depth, the optional hard mask of conductive materialis removed, and the via and trench depths are completed.

FIG. 8 illustrates computing device 300 in accordance with oneimplementation. Computing device 300 houses board 302. Board 302 mayinclude a number of components, including but not limited to a processor304 and at least one communication chip 306. Processor 304 is physicallyand electrically connected to board 302. In some implementations the atleast one communication chip 306 is also physically and electricallyconnected to board 302. In further implementations, the communicationchip 306 is part of processor 304.

Depending on its applications, computing device 300 may include othercomponents that may or may not be physically and electrically coupled toboard 302. These other components include, but are not limited to,volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flashmemory, a graphics processor, a digital signal processor, a cryptoprocessor, a chipset, an antenna, a display, a touchscreen display, atouchscreen controller, a battery, an audio codec, a video codec, apower amplifier, a global positioning system (GPS) device, a compass, anaccelerometer, a gyroscope, a speaker, a camera, and a mass storagedevice (such as hard disk drive, compact disk (CD), digital versatiledisk (DVD), and so forth).

Communication chip 306 enables wireless communications for the transferof data to and from computing device 300. The term “wireless” and itsderivatives may be used to describe circuits, devices, systems, methods,techniques, communications channels, etc., that may communicate datathrough the use of modulated electromagnetic radiation through anon-solid medium. The term does not imply that the associated devices donot contain any wires, although in some embodiments they might not.Communication chip 306 may implement any of a number of wirelessstandards or protocols, including but not limited to Wi-Fi (IEEE 802.11family), WiMAX (IEEE 802.16 family), IEEE 802.20, long term evolution(LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE, GSM, GPRS, CDMA, TDMA, DECT,Bluetooth, derivatives thereof, as well as any other wireless protocolsthat are designated as 3G, 4G, 5G, and beyond. Computing device 300 mayinclude a plurality of communication chips 306. For instance, a firstcommunication chip may be dedicated to shorter range wirelesscommunications such as Wi-Fi and Bluetooth and a second communicationchip may be dedicated to longer range wireless communications such asGPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others.

Processor 304 of computing device 300 includes an integrated circuit diepackaged within processor 304. In some implementations, the integratedcircuit die of the processor includes one or more devices, such astransistors or interconnectors, that are formed in accordance withimplementations described above where one or more dielectric layers(ILD) are covered with a dielectric hard mask that may be retained inthe final circuit die structure. The term “processor” may refer to anydevice or portion of a device that processes electronic data fromregisters and/or memory to transform that electronic data into otherelectronic data that may be stored in registers and/or memory.

The communication chip 306 also includes an integrated circuit diepackaged within the communication chip 306. In accordance with anotherimplementation of the invention, the integrated circuit die of thecommunication chip includes one or more devices, such as transistors orinterconnectors, that are formed in accordance with implementationsdescribed above incorporating a dielectric hard mask on one or moredielectric layers.

In further implementations, another component housed within thecomputing device 300 may contain an integrated circuit die that includesone or more devices, such as transistors or interconnectors, that areformed in accordance with implementations described above incorporatinga dielectric hard mask on one or more dielectric layers.

In various implementations, computing device 300 may be a laptop, anetbook, a notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a mobile phone, a desktopcomputer, a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player,or a digital video recorder. In further implementations, computingdevice 300 may be any other electronic device that processes data.

In the description above, for the purposes of explanation, numerousspecific details have been set forth in order to provide a thoroughunderstanding of the embodiments. It will be apparent however, to oneskilled in the art, that one or more other embodiments may be practicedwithout some of these specific details. The particular embodimentsdescribed are not provided to limit the invention but to illustrate it.The scope of the invention is not to be determined by the specificexamples provided above but only by the claims below. In otherinstances, well-known structures, devices, and operations have beenshown in block diagram form or without detail in order to avoidobscuring the understanding of the description. Where consideredappropriate, reference numerals or terminal portions of referencenumerals have been repeated among the figures to indicate correspondingor analogous elements, which may optionally have similarcharacteristics.

It should also be appreciated that reference throughout thisspecification to “one embodiment”, “an embodiment”, “one or moreembodiments”, or “different embodiments”, for example, means that aparticular feature may be included in the practice of the invention.Similarly, it should be appreciated that in the description variousfeatures are sometimes grouped together in a single embodiment, figure,or description thereof for the purpose of streamlining the disclosureand aiding in the understanding of various inventive aspects. Thismethod of disclosure, however, is not to be interpreted as reflecting anintention that the invention requires more features than are expresslyrecited in each claim. Rather, as the following claims reflect,inventive aspects may lie in less than all features of a singledisclosed embodiment. Thus, the claims following the DetailedDescription are hereby expressly incorporated into this DetailedDescription, with each claim standing on its own as a separateembodiment of the invention.

1. A method comprising: forming a dielectric layer on a contact point ofan integrated circuit structure; forming a hardmask comprising adielectric material on a surface of the dielectric layer; and forming atleast one via in the dielectric layer to the contact point using thehardmask as a pattern.
 2. The method of claim 1, wherein the dielectricmaterial of the hardmask comprises a dielectric constant greater than adielectric constant of silicon dioxide.
 3. The method of claim 1,wherein the dielectric material of the hardmask has a density that isgreater than a dielectric material of the dielectric layer.
 4. Themethod of claim 2, wherein the dielectric material of the hardmask isselected from the group consisting of silicon oxynitride, hafnium oxide,zirconium oxide, hafnium silicate, hafnium oxynitride and lanthanumoxide.
 5. The method of claim 2, wherein a material of the dielectriclayer comprises a dielectric constant less than a dielectric constant ofsilicon dioxide.
 6. The method of claim 2, wherein a material of thedielectric layer is porous.
 7. The method of claim 1, wherein thehardmask is a first hardmask, the method further comprising: forming asecond hardmask comprising a conductive material on the first hardmask;and forming at least one trench in the dielectric layer.
 8. The methodof claim 7, wherein after forming the at least one trench, removing thesecond hardmask.
 9. The method of claim 1, further comprising, afterforming the at least one via to the contact point, forming aninterconnect in the via with the hardmask remaining on the dielectriclayer.
 10. A method comprising: forming a dielectric layer comprising afirst low K dielectric material on a contact point of an integratedcircuit structure; and forming a hardmask comprising a second high Kdielectric material on a surface of the dielectric layer; patterning thehardmask for at least one trench; forming the at least one trench in thedielectric layer; after forming the at least one trench, forming atleast one via in the dielectric layer to the contact point; and formingan interconnect in the via to the contact point with the hardmaskremaining on the dielectric layer.
 11. The method of claim 10, whereinthe second high K dielectric material of the hardmask has a density thatis greater than the first low K dielectric material of the dielectriclayer.
 12. The method of claim 10, wherein the second high K dielectricmaterial of the hardmask is selected from the group consisting ofsilicon oxynitride, hafnium oxide, zirconium oxide, hafnium silicate,hafnium oxynitride and lanthanum oxide.
 13. The method of claim 10,wherein the hardmask is a first hardmask, the method further comprising:prior to patterning the hardmask for at least one trench, forming asecond hardmask comprising a conductive material on the first hardmask.14. The method of claim 13, wherein after forming the at least onetrench, removing the second hardmask.
 15. An apparatus comprising: acircuit substrate comprising at least one active layer including acontact point; a dielectric layer on the at least one active layer; ahardmask comprising a dielectric material having a least one openingtherein for an interconnect material; and an interconnect material inthe at least one opening of the hardmask and through the dielectriclayer to the contact point.
 16. The apparatus of claim 15, wherein thedielectric layer comprises a material having a dielectric constant lessthan a dielectric constant of silicon dioxide and the dielectricmaterial of the hardmask has a dielectric constant greater than adielectric constant of silicon dioxide.
 17. The apparatus of claim 16,wherein the dielectric material of the hardmask has a density greaterthan a density of the dielectric material of the dielectric layer. 18.The apparatus of claim 16, wherein the dielectric material of thehardmask is selected from the group consisting of silicon oxynitride,hafnium oxide, zirconium oxide, hafnium silicate, hafnium oxynitride andlanthanum oxide.